1. Field of the Invention
The present invention relates generally to an antenna, and more particularly to a multi-band inverted-F antenna which can be used with an electronic device and allows the electronic device to communicate within different frequency bands.
2. Description of the Prior Art
With the development of wireless local area networks (WLANs) and wireless personal area networks (WPANs) in the recent years, many protocols or standards are developed to adapt to the newest wireless networks accompanyingly. 802.11b, 802.11g, HomeRF, Zigbee which appears in 2003 and is developing rapidly now, Bluetooth1.0, and Bluetooth 2.0 which is under research now all require a working frequency in 2.4 GHz band. Meanwhile, 802.11a which is put forward in 2000 and 802.11n which is still a plan now all require a working frequency in 5 GHz band.
To match the wireless networks requirement and the standards mentioned above, many portable terminals have employed a number of different types of antennas to receive and transmit signals over the air interface. As known, the development of multi-band antennas embedded in wireless network devices is a newest trend. For example, planar inverted-F antennas mounted perpendicularly to a conducting portion have been found to implement dual-band easily, and also have advantage of good radiation characteristics, simple construction and relatively light weight.
In nowadays, many multi-band planar inverted-F antennas solutions are put forward. For example, referring to FIG. 9, U.S. Pat. No. 6,166,694 discloses a built-in multi-band planar inverted-F antenna suitable for using in future compact mobile terminals comprising a dielectric substrate 320, an antenna feed pin 325, a grounded post 335, two spiral arms 305 and 310 operating in different frequency bands and a matching bridge 330 positioned between the feed pin 325 and the grounded post 335. The conventional antenna is a microstrip antenna designed especially to work on GSM, DCS and ISM frequency bands. However, though it appears as a multi-band antenna, there is still a hope of an antenna that can work at higher dual-frequency, especially both at 2.4 GHz and 5 GHz bands so as to apply in different wireless local or wireless personal area networks and doesn't raise price. Further more, because the conventional antenna is manufactured as printed circuit, the configuration of the antenna is not steady enough to stand the resistance test.
Hence, synthetically consider the factors of frequency, configuration, fixing, stability, and occupancy space, etc, an improved multi-band inverted-F antenna is desired to overcome the above-mentioned disadvantages of the prior art.